| 摘要 |
1480858 Data transmission; ciphering INTERNATIONAL BUSINESS MACHINES CORP 24 Nov 1975 [24 Feb 1975] 48153/75 Heading H4P In apparatus for ciphering blocks of data bits under the control of a set of cipher key bits, such a block, e.g. of 32 bits, is first stored, and the set of key bits linearly transformed to provide a permuted set of, for example, 48 bits. Predetermined ones of the stored data bits are then duplicated to provide an expanded block having bits equal in number to the number of permuted cipher bits. The bits in the expanded block are then combined with the permuted cipher bits, e.g. by modulo-2 addition, and the result is non-linearly transformed to provide a substitution set of bits equal in number to the number of bits, e.g. 32, in the original block of data. Finally, the substitution set is linearly transformed to produce a product block cipher of the stored block of data bits. Suitable circuit arrangement for effecting the ciphering process are described with reference to Figs. 1 to 8 (not shown). |
